I dont know if this is a bug but i’ve run into this a few times, and it is very annoying to deal with.
Number variables that are not defined seem to be considered as “Not A Number”, and not Anything, which causes all calculations to fail (if < than, if > than, if ==, etc…) when used. Furthermore, i’ve discovered the only way to get them to identify as a Numeric variable at this point is by type-casting them with NUMBER(,) just to get them to be zero “0”, so they can be used in mathematical formulas.
I would expect that any unitialized number variable would have a default value of “0”, rather than Undefined or Not A Number, or anything useless. Just my opinion.